code: def testListDirectory(self):
      dir_path = os.path.join(self._base_dir, "test_dir")
      gfile.makedirs(dir_path)
      files = ["file1.txt", "file2.txt", "file3.txt"]
      for name in files:
          file_path = os.path.join(dir_path, name)
          gfile.GFile(file_path, mode="w").write("testing")
      subdir_path = os.path.join(dir_path, "sub_dir")
      gfile.makedirs(subdir_path)
      subdir_file_path = os.path.join(subdir_path, "file4.txt")
      gfile.GFile(subdir_file_path, mode="w").write("testing")
      dir_list = gfile.listdir(dir_path)
      self.assertCountEqual(files + ["sub_dir"], dir_list)
  
imports: import os.path
  from tensorboard import test
  from tensorboard.compat.tensorflow_stub import compat, errors
  from tensorboard.compat.tensorflow_stub.io import gfile
label_desc: Use image node_id 12 for calling the FileIoTest obj's underlying member method code with example usage: obj.testListDirectory() without return types